linux-kernel - Re: [RFC][PATCH 3/3] locking/qspinlock: Optimize for x86

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Message-ID: <20180927081314.GA8285@andrea>
Date:   Thu, 27 Sep 2018 10:13:15 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will.deacon@....com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, longman@...hat.com,
        tglx@...utronix.de
Subject: Re: [RFC][PATCH 3/3] locking/qspinlock: Optimize for x86

On Thu, Sep 27, 2018 at 09:59:35AM +0200, Peter Zijlstra wrote:
> On Thu, Sep 27, 2018 at 09:47:48AM +0200, Andrea Parri wrote:
> > > LKMM in particular does _NOT_ deal with mixed sized atomics _at_all_.
> > 
> > True, but it is nothing conceptually new to deal with: there're Cat
> > models that handle mixed-size accesses, just give it time.
> 
> Sure, but until that time I must not rely on (and thus not use) LKMM for
> qspinlock things.

This is way too generic to be agreed ;D


> 
> So while your argument about coherence might be true -- I'll have to
> think about it; litmus tests are out the window.

You trimmed the litmus test I gave you.

  Andrea